中国东部逆断层及油气

传统上把我国的沉积盆地划分为东部拉张,中部过渡,西部挤压,这种观点曾经束缚了人们的地震解释思路,在中国东部的剖面上出现逆断层现象而不能予以确定。事实上,中国东部总体上以拉张构造为主,普遍发育正断层,但在勘探中也确实发现了逆断层,且对油气聚集具有重要的控制作用。从成因观点分析,这些逆断层主要可分为构造挤压型及重力滑动型两大类。构造挤压型逆断层按地质时代又可分为晚第三纪、白垩纪、古生代末等三个时期,它们分别对应于中国东部大地构造演化的三个“断陷—坳陷”旋回,断陷对应于构造拉张期,坳陷对应干构造挤压期,逆断层主要发育于坳陷发育时期。着重对两类逆断层的形成机制、演化规律及油气赋存状态进行了论述剖析。中国东部含油气盆地的构造运动不是一张到顶的;晚第三纪的构造挤压逆冲断层与重力滑动逆冲断层在形成机理上是有区别的;逆同生断层在晚期干上覆地层中形成的浅层构造,应是次生油气藏的良好场所。

Reverse Faults and Hydrocarbon Accumulation in Eastern Part of China

In traditional,the tectonic pattern of sedimentary basins in China has been deemed as extension in the eastern part of Chi- na,transition in the center and compression in the western part,which has ever bound up the thought for seismic interpre- tation.In fact,although normal faults are commonly developed under the background of extension structures predominantly in the eastern part of China,reversed faults are often found dur- ing exploration and they even play an important role of control- ling hydrocarbon accumulation.In original classification,the reversed faults can be mainly divided into two Types: the structural compressive and the gravitation gliding.In time classification,the structural compressive reversed faults can be subdivided into the Neogene,the Cretaceous and the end- ing Paleozoic ones,which are respectively corresponding to the three cycles of“rift-faulting to depression” occurred during the tectonic evolutions in the eastern part of China.It is mainly discussed to the formation mechanism,evolution regularity and hydrocarbon existence situation of two types of reserved faults.It is has been made clear that not all the tectonic move- ments are extensional and some reverse thrusts may be ac- companied in petroliferous basins in eastern part of China.It is indicated that the Neogene reverse thrusts of tectonic exten- sion are different with those of gravitation gliding in formation mechanism.It is suggested that the shallow structures that overly the reverse contemporaneous faults during late phases should be the good places where secondary hydrocarbon-gen- erating reservoirs can form.